Remove the need to run NodeManager as privileged account for Windows Secure Container Executor

YARN-1972 introduces a Secure Windows Container Executor. However this executor requires the process launching the container to be LocalSystem or a member of the a local Administrators group. Since the process in question is the NodeManager, the requirement translates to the entire NM to run as a privileged account, a very large surface area to review and protect.

This proposal is to move the privileged operations into a dedicated NT service. The NM can run as a low privilege account and communicate with the privileged NT service when it needs to launch a container. This would reduce the surface exposed to the high privileges.

There has to exist a secure, authenticated and authorized channel of communication between the NM and the privileged NT service. Possible alternatives are a new TCP endpoint, Java RPC etc. My proposal though would be to use Windows LPC (Local Procedure Calls), which is a Windows platform specific inter-process communication channel that satisfies all requirements and is easy to deploy. The privileged NT service would register and listen on an LPC port (NtCreatePort, NtListenPort). The NM would use JNI to interop with libwinutils which would host the LPC client code. The client would connect to the LPC port (NtConnectPort) and send a message requesting a container launch (NtRequestWaitReplyPort). LPC provides authentication and the privileged NT service can use authorization API (AuthZ) to validate the caller.